#include <stdio.h>
#include <math.h>
int main() {
	double a,b,c;
	printf("Input a, b and c\n");
	scanf("%lf%lf%lf",&a,&b,&c);
	double s1=(a+b+c)/2;
	printf("Area: %lf\n",sqrt(s1*(s1-a)*(s1-b)*(s1-c)));
	return 0;
}